1. Field of the Invention
The present invention relates to a core bar for bending of a pipe and a method of bending of a pipe.
2. Description of the Related Art
One method of bending of a pipe typically involves use of a core bar in order to prevent collapse of the bent portion of the pipe; the tip of this core bar is made to face the location where the pipe is to be bent and bending of the pipe is then performed.
Also, in order to further prevent collapse of the bent portion of the pipe, a method of bending a pipe is known wherein a core bar as described above is employed and the interior of the pipe from the front of the core bar is packed with a filler (see for example Laid-open Japanese Patent Application No. H8-19821 (FIG. 1 and FIG. 2)).
However, with the above method of bending of a pipe using a core bar that is typically performed, when the bending angle of the pipe becomes large (the bending radius R after processing becomes small), a gap is nevertheless created between the tip of the core bar and the outer circumferential part of the pipe, and collapse of the outer circumferential part of the pipe occurs.
Also, in the case of the technique of preventing collapse of the pipe by packing the interior of the pipe in front of the core bar with a filler as described in Laid-open Japanese Patent Application No. H8-19821 (FIG. 1 and FIG. 2), a step of introducing the filler, means for holding the filler within the pipe in a condition with pressure applied thereto and a step of removing the filler from the pipe after bending are necessary; thus, in order to automate bending, bulky equipment becomes necessary and, in addition, it is not possible to completely prevent pipe collapse, since the filler is free to deform.